1. Field of the Invention
The present invention relates, generally, to systems, apparatuses and processes for securing electronic components or data and, in preferred embodiments, to a security module that encloses electronic components and protects against unauthorized access to the electronic components.
2. Description of Related Art
The security of data stored in electronic circuitry has become an important issue. Highly sensitive information such as financial data, PIN numbers, passwords, and access codes are frequently the target of unauthorized access by hackers.
It has been the purpose of software encryption/decryption methods to avoid such unauthorized access to sensitive programs or data by providing software keys which are stored in memory devices and are used to encrypt and decrypt sensitive programs or data. While this method has proven effective against software hackers, other methods of accessing sensitive programs or data remain a challenge.
One such method is the penetration of the physical package containing electronic components such as processors, logic circuits, or other circuits or components, as well as various memory devices used to store programs or data. Exposed address and data lines within the package may allow access to sensitive data. The penetration of the physical package may be brought about through chemicals, drilling, separation, etc. In addition, X-rays and other known techniques may allow non-destructive penetration into the physical package.
Many methods directed towards securing sensitive data against such physical penetration have been described. For example, U.S. Pat. No. 4,691,350 describes a device for securing microelectronic circuitry. An outer housing comprising individual ceramic plates surrounds a printed circuit board with microelectronic circuitry thereon and additional ceramic plates which form an inner housing around the printed circuit board. Each of the ceramic plates of the outer housing has, on its inner surface, superposed layers of conductive material separated by insulating layers.
The superposed layers include a “first conductive path segment” arranged in a winding configuration, “a conductive sheet,” and a “second conductive path segment” arranged in a winding configuration complementary to the winding configuration of the first conductive path. The conductive path segments on each given plate are serially connected to form a wire mesh segment associated with the plate. The conductive sheets and wire mesh segments on the plates of the outer housing are interconnected using interconnection blocks.
A voltage plane is connected between a supply voltage and a sensing circuit in the tamper detection circuit. The wire mesh is connected between a reference potential, such as ground, and a sensing circuit. According to the patent, an interruption in the wire mesh or a short of the wire mesh to the voltage plane caused by a tamper attempt may be detected by a low voltage detector in the tamper detection circuit. The tamper detection circuit also includes a low temperature detector which detects attempts at freezing CMOS memory cells.
U.S. Pat. Nos. 4,593,384; 4,807,284; and 4,811,288 describe other devices for securing microelectronic circuitry which employ similar rigid housings formed of plates having serpentine or meandering conductor paths. The devices comprise a plurality of separate plates which must be individually fabricated and subsequently assembled together using epoxy bonding.
The process of assembling these plates into a housing can be relatively complex. The various plates must be bonded together in a sequential manner and then the respective electrical connections must be formed using, for example, conductive epoxy. After the housing is assembled, non-conductive epoxy may be required along the lines between the adjacent parts to seal any gaps and provide additional strength to the housing. This process is not conducive to automated assembly procedures.
Other methods of securing sensitive data against such physical penetration have been described in other patents. For example, U.S. Pat. No. 5,353,350 describes an encapsulated polymer cradle to protect electronic circuitry from tampering. The polymer cradle comprises a transducer capable of generating a voltage in response to an alteration of pressure or temperature, and electronic means to detect the voltage and destroy sensitive data upon detection.
U.S. Pat. No. 5,998,858 describes a multi-layered interlaced conductive grid, which is integral to a microprocessor and hinders de-layering of the chip using chemical etching techniques or focused-ion beam methods.
U.S. Pat. No. 5,389,738 describes electrode finger grids which are provided above and below an integrated circuit die to detect physical attempts to penetrate the integrated circuit die.
U.S. Pat. No. 5,159,629 describes a screen material with fine conductive lines formed thereon in close proximity to each other. This screen material surrounds the electronic assembly to be protected. Changes in the resistance of the conductive lines will generate a signal which will cause the erasure of a memory containing secured data.
U.S. Pat. No. 5,117,457 describes a tamper-resistant package for protecting information stored in electronic circuitry. The package comprises an energy source which applies energy to an energy distribution system which surrounds the electronic circuitry. The energy distribution system comprises a path or paths for energy distribution. Sensing means are provided for sensing an intrusion into the energy distribution system.
While the methods for protecting electronic circuitry from unauthorized access which are discussed above may hinder hackers in their attempt to access sensitive data, they also have many limitations. Some involve complex components and assembly procedures which are not conducive to mass production. Others provide only partial protection by leaving unobstructed areas of the package vulnerable to physical attack.
In addition, without a method of easily varying the configuration of the protective devices, repeated studied attacks on a particular protective device may reveal ways to bypass the protections provided. U.S. Pat. No. 5,117,457, discussed above, describes methods of varying the path or paths for energy. However, the methods taught are complex.
Accordingly, there is a demand in the industry for a package for securing electronic components or data that provides a relatively high level of security and also has a design and configuration conducive to economical production processes such as automated mass production.